Various industries such as the automotive industry have been under increasing demand to produce engines that can operate on different fuels such as gasoline and alcohol. However, internal combustion engines must have selectively adjustable parameters for efficient combustion when operating using different fuels.
The majority of engines today are conventional in that they are designed specifically to operate with gasoline and are unable to accommodate alternative fuels such as alcohol. These conventional engines are restricted by the limitations in their control units which are programmed for gasoline parameters only. These parameters are used by the ECU to control the engine based on input from various sensors found throughout the vehicle.
Typical sensors used in a conventional gasoline engine include a throttle position, mass airflow, fuel pressure, engine temperature, oxygen, and others. Although there are differences between sensors used in various engines, the standard ECU uses them to continuously calculate optimum fuel flow rates to optimize combustion. The ECU does this by referencing predetermined fuel flow rates located in look up tables in its memory, which are cataloged by specific combinations of sensor data.
As sensor data changes in real time, the ECU calculates variations to predetermined fuel flow rates, and provides them to the fuel injector(s) in a continuous stream of timing command signals, i.e. changes to injector fuel pulse width. The larger the fuel pulse width, the longer the injector(s) is open, yielding greater fuel flow, and vice versa. These variations to injector command signals cause changes in the combustion occurring in the cylinders, which in turn leads to new sensor data received by the ECU, and the process repeats. This repeating process forms a closed loop operation in which the ECU establishes and sustains optimized combustion.
As a safety measure to guard against malfunction, fuel flow variations commanded by standard ECUs are limited to a maximum variation from their fuel flow look up tables. For systems intended for gasoline-only, this limitation is typically in the order of a 10% to 20% maximum variation, depending on the year, make and model of each particular system. Although the ECU is otherwise capable of arriving at optimal fuel flow rates above this limitation, the limitation stands as the restrictive maximum and is sufficient for fuels comprised mostly of gasoline.
In cases where fuels of lower energy density than gasoline are used, such as alcohol or alcohol/gasoline blends with significant alcohol concentration, fuel flow variations greater than the limitation are required. In such cases, the ECU will typically illuminate the check engine light and the engine will run rough or fail to run.
This creates the need for additional variations to the fuel injector command signals to enable successful operation with alcohol containing fuels. Therefore what is needed is an apparatus and method for modifying a conventional vehicle to run on alcohol containing fuels along with the ability to run using traditional gasoline formulations.